X-ray imaging has been used in the medical field and for radiology in general, such as non-destructive testing and x-ray computed tomography. Conventional radiology systems use x-ray absorption to distinguish differences between different materials, such as normal and abnormal human tissues.
Conventional x-ray imaging techniques, such as used in mammography, typically use a flood of x-rays to illuminate an object. A detection system, such as including a phosphor screen and a photographic film, is used to measure only the attenuation properties of the object by measuring the intensity of the x-rays that emerge from the object.
X-ray imaging for screening mammography has been used to identify early stages of breast cancer. It is well known that breast cancer mortality among women under screened controls can be significantly reduced when compared with unscreened controls. Mammography tends to identify smaller and less advanced stages of cancer, when compared with cancers found by breast physical examination or breast self-examination. Treatment of smaller and less advanced stages of breast cancer result in better survival rates. It is quite apparent that enhanced radiology methods can be used to detect even smaller and earlier stage breast cancers. Approximately 10% of clinically obvious breast cancers are not visible in images produced by conventional mammography methods. In addition, it is typically difficult to distinguish between benign lesions and malignant ones using conventional radiology.
In particular, breast cancer which is not visible with conventional mammography methods occurs most frequently in patients with relatively large amounts of breast glandular tissue. The density of the breast glandular tissue tends to obscure underlying pathology. In order to detect early stages of cancer, it is desirable to increase the sensitivity of mammography so that smaller and earlier stages of breast cancer can be detected. Earlier detection of breast cancer may result in significantly reduced mortality rates.
Mammographic technology has improved dramatically over the last two decades. For example, dedicated mammography equipment now exists with appropriate x-ray beam quality, adequate breast compression and automatic exposure control. However, conventional mammographic technology still depends upon the depiction of x-ray absorption to define differences between normal and abnormal tissues.
Limitations of conventional radiology are also apparent in imaging cartilage, such as during detection and treatment of injuries or degenerative joint diseases, such as osteoarthritis. Better imaging techniques would be beneficial for detecting such degenerative diseases earlier, such as before the point of irreversible damage.
Ingal et al., U.S. Pat. No. 5,319,694 discloses a method for obtaining an image of an internal structure of an object. Radiation transmitted through an object is collimated by a Laue type crystal analyzer. While deflecting the crystal analyzer, interferogram images of the internal structure of the object are monitored and a position of the crystal analyzer which provides an image with maximum contrast is selected. Both the transmitted beam and the diffracted beam emerging from the crystal analyzer carries information on the internal structure of the object. Simultaneous observation of the object in both the transmitted beam and the diffracted beam allows detection of artifacts in the image. Once the image is detected, the crystal analyzer is set to a position at which the maximum contrast of the object image is attained.
According to U.S. Pat. No. 5,319,694, simultaneous registering of images in a transmitted beam and a diffracted beam enables definition of minor and low-contrast image elements and elimination of errors in interpretation of the image due to the imperfection of the image detector. Algebraic addition of the transmitted image and the diffracted image enhances the contrast of the boundaries between different-density media, which is due to elimination of background resulting from photoelectric absorption of radiation in the object. A detector that detects the diffracted beam has a feedback loop output which is connected to a precision displacement actuator which moves the crystal analyzer.
There is an apparent need for mammographic and radiologic methods that can be used to detect even smaller and earlier stages of breast cancer, than the stages of breast cancer that can be detected with conventional imaging technology.
There is a need for improved radiologic methods that can be used to detect small changes in joint tissues, such as cartilage. There is also a need for a radiologic imaging method that can characterize materials, such as tissue, for research and treatment of diseases.
There is a need for an x-ray imaging method that provides clearer images on a pixel-by-pixel basis of an object. There is a need for an imaging method that provides images based upon x-ray properties other than absorption, such as refraction and scatter.